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: a sleeper playnoun
[the first noun sense may be fr gambling term sleeper, found by 1856 and meaning both ''an unexpected winning card'' and ''a pot whose owner has ignored it, and hence is free to anyone who takes it'']
any of the marine and freshwater fishes of the family Eleotridae of the suborder Gobioidei (order Perciformes). Sleepers, found in warm and tropical regions, are so named because most species habitually lie quietly on the bottom. They are elongated fishes with two dorsal fins and are distinguished from most other gobies in having their pelvic fins separate, rather than joined to form a weak, rounded suction cup